Apparatuses comprising various means for unwinding, forwarding, debossing or embossing, and/or perforating, and rewinding of a ribbon or web of thermoplastic film are disclosed in the prior art: see for instance, U.S. Pat. No. Re. 23,910, Method of And Apparatus For Producing Textured Films which issued Dec. 14, 1954 to L. H. Smith et al.; U.S. Pat. No. 3,054,148, Process Of Producing A Perforated Thermoplastic Sheet which issued Sep. 18, 1962 to W. F. Zimmerli; and U.S. Pat. No. 2,567,275, Apparatus And Method Of Goffering Thermoplastic-tic Materials which issued Sep. 11, 1951 to R. Colombo. See also U.S. Pat. No. 3,674,221, Dynamic Stress-Strain Testing Of Ribbons Of Film which issued Jul. 4, 1972 to Coenraad E. Riemersma.
The prior art also discloses various methods of making perforated members: see for instance U.S. Pat. No. 3,453,712, Method Of Making A Porous Roll which issued Jul. 8, 1969 to R. G. MacKendrick; U.S. Pat. No. 3,613,208, Method Of Fabricating A Perforated Panel For A Vacuum Work-Holder Or Chuck which issued Oct. 19, 1971 to H. A. Seberg et al.; and U.S. Pat. No. 3,247,579, Circuit Fabrication Method which issued Apr. 26, 1966 to L. H. Cattermole et al.
Methods and apparatuses for imparting a three-dimensional polymeric web having improved tactile impression are disclosed in U.S. Pat. No. 4,151,240, Method for Debossing and Perforating a Running Ribbon of Thermoplastic Film, which issued Apr. 24, 1979 to Lucas et al.; and U.S. Pat. No. 4,601,868, Method of Imparting a Three-Dimensional Fiber-Like Appearance and Tactile Impression to a Running Ribbon of Thermoplastic Film, which issued Jul. 22, 1986 to Radel et al. and U.S. Pat. No. 4,342,314, issued to Radel et al.
Other methods and apparatuses have been disclosed for making polymeric webs exhibiting a soft and silky tactile impression. For example, U.S. Pat. No. 4,609,518 and U.S. Pat. No. 4,629,643, each issued to Curro et al., and issued Sep. 2, 1986, and Dec. 16, 1986, respectively, disclose an apparatus for forming a polymeric web having large apertures and a plurality of fine-scale apertures.
The above-mentioned references are representative of various methods and apparatuses for embossing or debossing polymeric films on a supporting framework, often termed a forming structure or screen. In particular, many of these references disclose the use of cylindrical metal screens comprising an interconnecting network defining a plurality of apertures to which a polymeric film can conform when impinged upon by a fluid such as jets of water or heated air. The plurality of apertures provides for a relatively high open area through the screen through which water, for example, can pass through. One example of the use of such screens for the application of high pressure liquid jet or stream to a web of polymeric film is disclosed in U.S. Pat. No. 4,778,644, issued to Curro et al., and issued Oct. 18, 1988.
Metal forming structures, e.g., screens, of the type disclosed above in Radel et al. '314 can have surface aberrations on one surface thereof, as described in U.S. Pat. No. 4,463,045, issued Jul. 31, 1984 to Ahr et al. Ahr et al. discloses that the surface aberrations, or protuberances on a metal forming structure can be formed by a photoetching process involving the application of a resist coating that corresponds to the desired pattern of surface aberrations. Surface aberrations on a polymer film made on such a forming structure are disclosed as providing desirable tactile impression to a user.
The surface aberrations of the polymeric web disclosed in Ahr et al. '045 are taught as having an amplitude, i.e., a height, of at least about 0.2 mils (0.0002 inches) and at least about 0.3 mils (0.0003 inches). It is believed that having generally columnar, pillar-like surface aberrations on a metal forming structure having an amplitude of between about 1 mil (about 0.001 inch, about 25.4 mm) and 10 mils (about 0.010 inches, about 255 mm) would provide for a polymer web having much better tactile impression to a user. In particular, surface aberrations having such amplitudes in combination with cross-sectional dimensions resulting in an aspect ratio (amplitude/diameter) of between about 1 and 3 would produce a particularly soft-feeling polymeric web.
Attempts to make surface aberrations having significantly higher amplitudes on metal forming structures such as those described in Ahr '045 have been unsuccessful due to the inherent limitations of known photoetching processes. That is, after a resist coating is applied, photoetching, if given sufficient time, tends to etch away material around the surface aberrations indiscriminately, resulting in protrusions having a generally “mushroom-shaped” profile. Eventually, due to the undercutting effect of the photoetching, the base of the surface aberration can be completely etched away. If polymeric webs were to be formed over such a forming structure it is believed that they would be difficult to remove from the forming structure due to the mushroom-shaped protrusions.
Accordingly, there is a need for an improved metal forming structure useful for making three-dimensional formed film webs, such as for use as a topsheet in disposable absorbent articles.
Additionally, there is a need for a method of making improved metal forming structures having surface aberrations having relatively high aspect ratios.